Optical or conductive mark scanning systems of several types used to read and record large amounts of data very quickly are well known in the prior art. Such systems are typically used to process data from documents such as, for example, sheets of paper, cards, labels, tags, or other material. Generally speaking, some types of these documents have a plurality of pre-printed control marks (sometimes called "timing marks") in a control mark column (sometimes called a "timing track") used to trigger the system to scan or "read" certain data marks (also called "indicia") or data response areas (also called "indicia-receiving locations"). The data response areas are placed in a specified relation to the control marks. Usually, a firmware programmable read only memory (PROM) or software template and data processing means are used to keep track of control marks and data marks. The processing means will normally be programmed to work with a specific document format (e.g., it will expect a certain number of control marks and a certain pattern of data response areas in relation to the control marks).
At least two distinct optical scanning methods are used to detect the presence of indicia (e.g., data marks), control marks or other marks in data response areas (i.e., indicia-receiving locations). In one method, a light source placed at one surface of a document illuminates the area to be read and a photo-sensor placed at the opposite surface of the document is used to sense light that is transmitted through the document. The photo-sensor detects differences between the levels of light transmitted through marked and unmarked areas.
In another method, both the light source and the photo-sensor are located on the same side of the document that is scanned. The photo-sensor detects differences between the levels of light reflected by marked and unmarked areas when they are illuminated. In both methods, the output of the photo-sensor is processed electronically to determine the presence or absence of a mark.
Both methods have limitations that may affect the ability of a photo-sensing apparatus to accurately detect the information on data processing forms. One limitation is related to the placement of indicia (e.g., data marks) in the data response areas (i.e., indicia-receiving locations). Each indicia-receiving location may be outlined or otherwise designated by some sort of marking printed on certain types of data processing forms. In some embodiments, indicia is placed in the indicia-receiving locations by darkening the designated area or by printing or writing a response in alpha-numeric characters or other such characters as may be required.
Inaccurate responses may be generated by the photo-sensing apparatus if the markings that designate the indicia-receiving location interfere with the proper detection of indicia. As an example, scannable answer sheets, census forms and the like are filled-out by providing indicia within designated indicia-receiving locations. If the indicia overlap any markings used to designate the indicia-receiving locations, they might be improperly read by the photo-sensor.
Conventional photo-sensing apparatus, which may incorporate computer software and/or hardware, are often configured to inspect or "look" precisely at areas designated to contain indicia and not at other areas in order to discriminate between indicia (e.g., data marks), stray indicia (e.g., stray data marks), non-indicia (e.g., material not intended to be detected by photo-sensing apparatus), smudges, flaws in the document, or the like. Moreover, data processing forms may have applications where only a few indicia-receiving locations are expected to contain indicia. In those situations, photo-sensing apparatus can be designed or programmed to ignore indicia sensed in other areas. It is important that the data processing form be as free of clutter or markings which may interfere with the processing in order to simplify the design of the photo-sensing apparatus and to enhance the accuracy of processing. Accordingly, it is very desirable to eliminate or otherwise render undetectable any text, graphics, position markers (e.g., marks defining indicia-receiving locations), or other markings that should not be detected by the photo-sensing apparatus prior to processing.
Another limitation of conventional data processing form relates to the indicia. In many situations, it may be desirable to quickly and efficiently erase or modify the indicia that are to be detected by photo-sensing apparatus. For example, data processing forms containing indicia (e.g., dots, shapes, alpha-numeric characters, lines, bars or the like) in formats, such as, for example, coupons, packaging labels, parts labels, bar code labels or tags, assembly-line work-in-progress labels or tags, or other items are used in such large numbers that the cost of reprinting or replacing the forms on each item simply to modify the indicia could become significant.
Accordingly, there is a need for a data processing form that can be used with a photo-sensing apparatus without the problem of indicia overlapping the markings used to designate indicia-receiving locations. There is also a need for a data processing form that permits quick and efficient erasure or modification of the indicia that are to be detected by photo-sensing apparatus.